OSLO, May 12 (Reuters) - The habitats of many common plants and animals will shrink dramatically this century unless governments act quickly to cut rising greenhouse gas emissions, scientists said on Sunday after studying 50,000 species around the world.

The scientists from Britain, Australia and Colombia said plants, amphibians and reptiles were most vulnerable as global temperatures rise and rainfall patterns change.

About 57 percent of plants and 34 percent of animal species were likely to lose more than half the area with a climate suited to them by the 2080s if nothing was done to limit emissions from power plants, factories and vehicles, they wrote in the journal Nature Climate Change.

Hardest hit would be species in sub-Saharan Africa, Australia, the Amazon and Central America.

"Climate change will greatly reduce biodiversity, even for many common animals and plants," lead author Rachel Warren of the University of East Anglia in England said. The decline would damage natural services for humans such as water purification and pollination, she said.

But the scientists said governments could reduce the projected habitat loss by 60 percent if global greenhouse gas emissions peaked by 2016 and then fell. A peak by 2030 would cut losses by 40 percent.

Only 4 percent of animals, and no plants, were likely to benefit from rising temperatures and gain at least 50 percent extra territory, the study said.

However, some experts said while it was clear that global temperatures were rising, forecasting the effect on plants and animals was often unreliable as species range was difficult to check.

DIFFICULT BALANCE

Some past studies have indicated that creatures such as bats, hares or opossums may be more able to adapt to new climates than believed. Yet many species of frogs and toads are suffering worse declines in numbers than projected by computer models, apparently because a fungal skin disease is aggravating the effects of global warming.

"It's very difficult to get the right balance between crying wolf and examining the facts," said Carsten Dormann, professor at the Helmholtz Centre for Environmental Research in Germany, who was not involved in the study. "We simply don't know if these assessments are correct."

The scientists said: "Over half of common plants and one third of the animals could see a dramatic decline this century due to climate change." They said their findings were "probably conservative" as they did not take account of factors that could exacerbate declines, such as pests or diseases.

Almost 200 governments have agreed to limit global warming to less than 2 degrees C (3.6F) above pre-industrial times. They plan to agree, by the end of 2015, a deal to curb emissions.

Global average surface temperatures have risen by 0.8 degree C (1.4F) since the Industrial Revolution.

The amount of carbon dioxide, a greenhouse gas, in the atmosphere topped 400 parts per million for the first time since measurements began in 1958, the U.S. National Oceanic and Atmospheric Administration said on Friday.

A U.N. panel of climate scientists says it is at least 90 percent likely that human activities, rather than natural variations, are the main cause of warming since about 1950.

For the report: (http://dx.doi.org/10.1038/nclimate1887) (Reporting By Alister Doyle; Editing by Janet Lawrence)

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